<html>
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        var i=1,j,k;
        j=i;
        ++i;
        console.log(j);//输出1
        console.log(i);//输出2
        k=i;
        --i;
        console.log(k);//输出2
        console.log(i);//输出1
    </script>
</body>
</html>